1. Field of the Inventions
The present inventions relate to multiple disc clutch apparatuses, such as clutches provided with a clutch piston which can be displaced toward a clutch-on side by oil supplied to an oil pressure chamber to pressure-contact driving clutch plates and driven clutch plates with each other.
2. Description of the Related Art
There are two types of power transmitting apparatus for selectively transmitting or cutting off a power of an engine to or from wheels such as a manual transmission (MT) manually operating speed change of a vehicle and an automatic transmission (AT) automatically operating the speed change. The AT can easily perform speed change operations, however it is inferior in operation response due to its use of a torque converter. On the other hand, the MT is superior in the operation response, however it is liable to cause shocks during speed change operations.
In view of reduction of the speed change shocks and of improvement of speed change response, Japanese Laid-open Patent Publication No. 341652/1992 describes a multiple disc clutch apparatus provided with a plurality of clutch members. The multiple disc clutch apparatus of this prior art reference has a clutch piston arranged with its one surface facing toward an oil pressure chamber and the other surface being facing toward driving clutch plates or driven clutch plates. In such a multiple disc clutch apparatus, control of the clutch can be automatically performed in accordance with a velocity of vehicle and thus automatic speed changing operation can be carried out without causing a large shock in the speed changing operation.
The clutch piston of the prior art is so constructed that it can be displaced toward a clutch-on side by oil supplied to an oil pressure chamber to pressure-contact driving clutch plates and driven clutch plates each other so as to transmit a driving force of an input member to an output member and also can be returned toward a clutch-off side by discharging the oil in the oil pressure chamber to separate the driving and driven clutch plates from each other so as to cut off the transmission of driving force from the input member to the output member.
The clutch piston of the prior art also has a check valve adapted to occupy a closed condition for preventing the oil from flowing from the oil pressure chamber to the side of other surface of the clutch piston when the clutch apparatus is clutched on and also adapted to occupy an opened condition for allowing flow of air from the side of other surface to the oil pressure chamber when the clutch apparatus is clutched-off.